Role of Zookeeper in Kafka

1. Brokers registration, with heartbeats mechanism to keep the list current

2. Maintaining a list of topics alongside

    - Their configuration (partitions, replication factor, additional configurations..)

    - The list of ISRs (in sync replicas) for partitions

3.  Performing leader elections in case some brokers go down

4. Storing the Kafka cluster id(randomly generated at 1st startup of cluster)

5. Storing ACLs (Access Control Lists) if security is enabled

    - Topics

    - Consumer Groups

    - Users

6. Quatas configuration if enabled

7. (deprecated) Used by old consumer API to store consumer offserts